Method and apparatus for generating reference signal sequence in wireless communication system

ABSTRACT

A user equipment (UE) for receiving information on a length of a reference signal (RS) sequence and information on an offset of the RS sequence and performing an RS sequence mapping to map the RS sequence to a physical resource block 0 (PRB0) of the UE within a bandwidth part (BWP) based on the length of the RS sequence and the offset of the RS sequence. The UE also transmits, to the network, the RS sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/646,131, filed on Mar. 10, 2020, which is the National Stage filingunder 35 U.S.C. 371 of International Application No. PCT/KR2018/011690,filed on Oct. 2, 2018, which claims the benefit of U.S. ProvisionalApplication No. 62/567,126, filed on Oct. 2, 2017, the contents of whichare all hereby incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for generating a referencesignal (RS) sequence in a wireless communication system, specifically ina new radio access technology (RAT) system.

BACKGROUND

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPPto develop requirements and specifications for new radio (NR) systems.3GPP has to identify and develop the technology components needed forsuccessfully standardizing the new RAT timely satisfying both the urgentmarket needs, and the more long-term requirements set forth by the ITUradio communication sector (ITU-R) international mobiletelecommunications (IMT)-2020 process. Further, the NR should be able touse any spectrum band ranging at least up to 100 GHz that may be madeavailable for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usagescenarios, requirements and deployment scenarios including enhancedmobile broadband (eMBB), massive machine-type-communications (mMTC),ultra-reliable and low latency communications (URLLC), etc. The NR shallbe inherently forward compatible.

SUMMARY

It may be required to enhance a method for generating a reference signal(RS) sequence.

In an aspect, a method for generating a reference signal (RS) sequenceby a user equipment (UE) in a wireless communication system is provided.The method includes receiving information on a length of the RS sequenceand information on an offset of the RS sequence from a network, andgenerating the RS sequence based on the information on the length andthe information on the offset.

In another aspect, a user equipment (UE) in a wireless communicationsystem is provided. The UE includes a memory, a transceiver, and aprocessor, operably coupled to the memory and the transceiver, thatcontrols the transceiver to receive information on a length of areference signal (RS) sequence and information on an offset of the RSsequence from a network, and generates the RS sequence based on theinformation on the length and the information on the offset.

In another aspect, a method for receiving a reference signal (RS)sequence by a base station (BS) in a wireless communication system isprovided. The method includes transmitting information on a length ofthe RS sequence and information on an offset of the RS sequence to auser equipment (UE), and receiving the RS sequence, which is generatedbased on the information on the length and the information on theoffset, from the UE.

RS sequence can be generated based on configured length and/or offset ofthe RS sequence, instead of common PRB indexing. Signaling overhead canbe avoided, and network flexibility can be supported.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a wireless communication system to whichtechnical features of the present invention can be applied.

FIG. 2 shows another example of a wireless communication system to whichtechnical features of the present invention can be applied.

FIG. 3 shows an example of a frame structure to which technical featuresof the present invention can be applied. I

FIG. 4 shows another example of a frame structure to which technicalfeatures of the present invention can be applied.

FIG. 5 shows an example of a resource grid to which technical featuresof the present invention can be applied.

FIG. 6 shows an example of a synchronization channel to which technicalfeatures of the present invention can be applied.

FIG. 7 shows an example of a frequency allocation scheme to whichtechnical features of the present invention can be applied.

FIG. 8 shows an example of multiple BWPs to which technical features ofthe present invention can be applied.

FIG. 9 shows a method for generating a RS sequence by a UE according toan embodiment of the present invention.

FIG. 10 shows a UE to implement an embodiment of the present invention.

FIG. 11 shows a method receiving a RS sequence by a BS according to anembodiment of the present invention.

FIG. 12 shows a BS to implement an embodiment of the present invention.

DETAILED DESCRIPTION

The technical features described below may be used by a communicationstandard by the 3rd generation partnership project (3GPP)standardization organization, a communication standard by the instituteof electrical and electronics engineers (IEEE), etc. For example, thecommunication standards by the 3GPP standardization organization includelong-term evolution (LTE) and/or evolution of LTE systems. The evolutionof LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G newradio (NR). The communication standard by the IEEE standardizationorganization includes a wireless local area network (WLAN) system suchas IEEE 802.11a/b/g/n/ac/ax. The above system uses various multipleaccess technologies such as orthogonal frequency division multipleaccess (OFDMA) and/or single carrier frequency division multiple access(SC-FDMA) for downlink (DL) and/or uplink (DL). For example, only OFDMAmay be used for DL and only SC-FDMA may be used for UL. Alternatively,OFDMA and SC-FDMA may be used for DL and/or UL.

FIG. 1 shows an example of a wireless communication system to whichtechnical features of the present invention can be applied.Specifically, FIG. 1 shows a system architecture based on anevolved-UMTS terrestrial radio access network (E-UTRAN). Theaforementioned LTE is a part of an evolved-UTMS (e-UMTS) using theE-UTRAN.

Referring to FIG. 1 , the wireless communication system includes one ormore user equipment (UE; 10), an E-UTRAN and an evolved packet core(EPC). The UE 10 refers to a communication equipment carried by a user.The UE 10 may be fixed or mobile. The UE 10 may be referred to asanother terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more base station (BS) 20. The BS 20provides the E-UTRA user plane and control plane protocol terminationstowards the UE 10. The BS 20 is generally a fixed station thatcommunicates with the UE 10. The BS 20 hosts the functions, such asinter-cell radio resource management (MME), radio bearer (RB) control,connection mobility control, radio admission control, measurementconfiguration/provision, dynamic resource allocation (scheduler), etc.The BS may be referred to as another terminology, such as an evolvedNodeB (eNB), a base transceiver system (BTS), an access point (AP), etc.

A downlink (DL) denotes communication from the BS 20 to the UE 10. Anuplink

(UL) denotes communication from the UE 10 to the BS 20. A sidelink (SL)denotes communication between the UEs 10. In the DL, a transmitter maybe a part of the BS 20, and a receiver may be a part of the UE 10. Inthe UL, the transmitter may be a part of the UE 10, and the receiver maybe a part of the BS 20. In the SL, the transmitter and receiver may be apart of the UE 10.

The EPC includes a mobility management entity (MME), a serving gateway(S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts thefunctions, such as non-access stratum (NAS) security, idle statemobility handling, evolved packet system (EPS) bearer control, etc. TheS-GW hosts the functions, such as mobility anchoring, etc. The S-GW is agateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 30will be referred to herein simply as a “gateway,” but it is understoodthat this entity includes both the MME and S-GW. The P-GW hosts thefunctions, such as UE Internet protocol (IP) address allocation, packetfiltering, etc. The P-GW is a gateway having a PDN as an endpoint. TheP-GW is connected to an external network.

The UE 10 is connected to the BS 20 by means of the Uu interface. TheUEs 10 are interconnected with each other by means of the PC5 interface.The BSs 20 are interconnected with each other by means of the X2interface. The BSs 20 are also connected by means of the S1 interface tothe EPC, more specifically to the MME by means of the S1-MME interfaceand to the S-GW by means of the S1-U interface. The S1 interfacesupports a many-to-many relation between MMEs/S-GWs and BSs.

FIG. 2 shows another example of a wireless communication system to whichtechnical features of the present invention can be applied.Specifically, FIG. 2 shows a system architecture based on a 5G new radioaccess technology (NR) system. The entity used in the 5G NR system(hereinafter, simply referred to as “NW”) may absorb some or all of thefunctions of the entities introduced in FIG. 1 (e.g. eNB, MME, S-GW).The entity used in the NR system may be identified by the name “NG” fordistinction from the LTE.

Referring to FIG. 2 , the wireless communication system includes one ormore UE 11, a next-generation RAN (NG-RAN) and a 5th generation corenetwork (5GC). The NG-RAN consists of at least one NG-RAN node. TheNG-RAN node is an entity corresponding to the BS 10 shown in FIG. 1 .The NG-RAN node consists of at least one gNB 21 and/or at least oneng-eNB 22. The gNB 21 provides NR user plane and control plane protocolterminations towards the UE 11. The ng-eNB 22 provides E-UTRA user planeand control plane protocol terminations towards the UE 11.

The 5GC includes an access and mobility management function (AMF), auser plane function (UPF) and a session management function (SMF). TheAMF hosts the functions, such as NAS security, idle state mobilityhandling, etc. The AMF is an entity including the functions of theconventional MME. The UPF hosts the functions, such as mobilityanchoring, protocol data unit (PDU) handling. The UPF an entityincluding the functions of the conventional S-GW. The SMF hosts thefunctions, such as UE IP address allocation, PDU session control.

The gNBs and ng-eNBs are interconnected with each other by means of theXn interface. The gNBs and ng-eNBs are also connected by means of the NGinterfaces to the 5GC, more specifically to the AMF by means of the NG-Cinterface and to the UPF by means of the NG-U interface.

A structure of a radio frame in NR is described. In LTE/LTE-A, one radioframe consists of 10 subframes, and one subframe consists of 2 slots. Alength of one subframe may be 1 ms, and a length of one slot may be 0.5ms. Time for transmitting one transport block by higher layer tophysical layer (generally over one subframe) is defined as atransmission time interval (TTI). A TTI may be the minimum unit ofscheduling.

Unlike LTE/LTE-A, NR supports various numerologies, and accordingly, thestructure of the radio frame may be varied. NR supports multiplesubcarrier spacings in frequency domain. Table 1 shows multiplenumerologies supported in NR. Each numerology may be identified by index

TABLE 1 Subcarrier Supported for Supported for μ spacing (kHz) Cyclicprefix data synchronization 0 15 Normal Yes Yes 1 30 Normal Yes Yes 2 60Normal, Yes No Extended 3 120 Normal Yes Yes 4 240 Normal No Yes

Referring to Table 1, a subcarrier spacing may be set to any one of 15,30, 60, 120, and 240 kHz, which is identified by index However,subcarrier spacings shown in Table 1 are merely exemplary, and specificsubcarrier spacings may be changed. Therefore, each subcarrier spacing(e.g. μ=0,1 . . . 4) may be represented as a first subcarrier spacing, asecond subcarrier spacing . . . Nth subcarrier spacing.

Referring to Table 1, transmission of user data (e.g. physical uplinkshared channel (PUSCH), physical downlink shared channel (PDSCH)) maynot be supported depending on the subcarrier spacing. That is,transmission of user data may not be supported only in at least onespecific subcarrier spacing (e.g. 240 kHz).

In addition, referring to Table 1, a synchronization channel (e.g. aprimary synchronization signal (PSS), a secondary synchronization signal(SSS), a physical broadcast channel (PBCH)) may not be supporteddepending on the subcarrier spacing. That is, the synchronizationchannel may not be supported only in at least one specific subcarrierspacing (e.g. 60 kHz).

In NR, a number of slots and a number of symbols included in one radioframe/subframe may be different according to various numerologies, i.e.various subcarrier spacings. Table 2 shows an example of a number ofOFDM symbols per slot, slots per radio frame, and slots per subframe fornormal cyclic prefix (CP).

TABLE 2 Number of symbols Number of slots Number of slots μ per slot perradio frame per subframe 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14160 16

Referring to Table 2, when a first numerology corresponding to μ=0 isapplied, one radio frame includes 10 subframes, one subframe correspondsto one slot, and one slot consists of 14 symbols. In the presentspecification, a symbol refers to a signal transmitted during a specifictime interval. For example, a symbol may refer to a signal generated byOFDM processing. That is, a symbols in the present specification mayrefer to an OFDM/OFDMA symbol, or SC-FDMA symbol, etc. A CP may belocated between each symbol.

FIG. 3 shows an example of a frame structure to which technical featuresof the present invention can be applied. In FIG. 3 , a subcarrierspacing is 15 kHz, which corresponds to μ=0.

FIG. 4 shows another example of a frame structure to which technicalfeatures of the present invention can be applied. In FIG. 4 , asubcarrier spacing is 30 kHz, which corresponds to μ=1.

Table 3 shows an example of a number of OFDM symbols per slot, slots perradio frame, and slots per subframe for extended CP.

TABLE 3 Number of symbols Number of slots Number of slots μ per slot perradio frame per subframe 2 12 40 4

Meanwhile, a frequency division duplex (FDD) and/or a time divisionduplex (TDD) may be applied to a wireless system to which an embodimentof the present invention is applied. When TDD is applied, in LTE/LTE-A,UL subframes and DL subframes are allocated in units of subframes.

In NR, symbols in a slot may be classified as a DL symbol (denoted byD), a flexible symbol (denoted by X), and a UL symbol (denoted by U). Ina slot in a DL frame, the UE shall assume that DL transmissions onlyoccur in DL symbols or flexible symbols. In a slot in an UL frame, theUE shall only transmit in UL symbols or flexible symbols.

Table 4 shows an example of a slot format which is identified by acorresponding format index. The contents of the Table 4 may be commonlyapplied to a specific cell, or may be commonly applied to adjacentcells, or may be applied individually or differently to each UE.

TABLE 4 For- Symbol number in a slot mat 0 1 2 3 4 5 6 7 8 9 10 11 12 130 D D D D D D D D D D D D D D 1 U U U U U U U U U U U U U U 2 X X X X XX X X X X X X X X 3 D D D D D D D D D D D D D X 4 D D D D D D D D D D DD X X 5 D D D D D D D D D D D X X X 6 D D D D D D D D D D X X X X 7 D DD D D D D D D X X X X X 8 X X X X X X X X X X X X X U 9 X X X X X X X XX X X X U U 10 X U U U U U U U U U U U U U 11 X X U U U U U U U U U U UU 12 X X X U U U U U U U U U U U 13 X X X X U U U U U U U U U U 14 X X XX X U U U U U U U U U 15 X X X X X X U U U U U U U U 16 D X X X X X X XX X X X X X 17 D D X X X X X X X X X X X X 18 D D D X X X X X X X X X XX 19 D X X X X X X X X X X X X U 20 D D X X X X X X X X X X X U 21 D D DX X X X X X X X X X U 22 D X X X X X X X X X X X U U 23 D D X X X X X XX X X X U U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .

For convenience of explanation, Table 4 shows only a part of the slotformat actually defined in NR. The specific allocation scheme may bechanged or added.

The UE may receive a slot format configuration via a higher layersignaling (i.e.

radio resource control (RRC) signaling). Or, the UE may receive a slotformat configuration via downlink control information (DCI) which isreceived on PDCCH. Or, the UE may receive a slot format configurationvia combination of higher layer signaling and DCI.

FIG. 5 shows an example of a resource grid to which technical featuresof the present invention can be applied. An example shown in FIG. 5 is atime-frequency resource grid used in NR. An example shown in FIG. 5 maybe applied to UL and/or DL. Referring to FIG. 5 , multiple slots areincluded within one subframe on the time domain. Specifically, whenexpressed according to the value of “μ”, “14.2μ,” symbols may beexpressed in the resource grid. Also, one resource block (RB) may occupy12 consecutive subcarriers. One RB may be referred to as a physicalresource block (PRB), and 12 resource elements (REs) may be included ineach PRB. The number of allocatable RBs may be determined based on aminimum value and a maximum value. The number of allocatable RBs may beconfigured individually according to the numerology (“μ”). The number ofallocatable RBs may be configured to the same value for UL and DL, ormay be configured to different values for UL and DL.

A cell search scheme in NR is described. The UE may perform cell searchin order to acquire time and/or frequency synchronization with a celland to acquire a cell identifier (ID). Synchronization channels such asPSS, SSS, and PBCH may be used for cell search.

FIG. 6 shows an example of a synchronization channel to which technicalfeatures of the present invention can be applied. Referring to FIG. 6 ,the PSS and SSS may include one symbol and 127 subcarriers. The PBCH mayinclude 3 symbols and 240 subcarriers.

The PSS is used for synchronization signal/PBCH block (SSB) symboltiming acquisition. The PSS indicates 3 hypotheses for cell IDidentification. The SSS is used for cell ID identification. The SSSindicates 336 hypotheses. Consequently, 1008 physical layer cell IDs maybe configured by the PSS and the SSS.

The SSB block may be repeatedly transmitted according to a predeterminedpattern within the 5ms window. For example, when L SSB blocks aretransmitted, all of SSB #1 through SSB #L may contain the sameinformation, but may be transmitted through beams in differentdirections. That is, quasi co-located (QCL) relationship may not beapplied to the SSB blocks within the 5 ms window. The beams used toreceive the SSB block may be used in subsequent operations between theUE and the network (e.g. random access operations). The SSB block may berepeated by a specific period. The repetition period may be configuredindividually according to the numerology.

Referring to FIG. 6 , the PBCH has a bandwidth of 20 RBs for the 2nd/4thsymbols and 8 RBs for the 3rd symbol. The PBCH includes a demodulationreference signal (DM-RS) for decoding the PBCH. The frequency domain forthe DM-RS is determined according to the cell ID. Unlike LTE/LTE-A,since a cell-specific reference signal (CRS) is not defined in NR, aspecial DM-RS is defined for decoding the PBCH (i.e. PBCH-DMRS). ThePBCH-DMRS may contain information indicating an SSB index.

The PBCH performs various functions. For example, the PBCH may perform afunction of broadcasting a master information block (MIB). Systeminformation (SI) is divided into a minimum SI and other SI. The minimumSI may be divided into MIB and system information block type-1 (SIB1).The minimum SI excluding the MIB may be referred to as a remainingminimum SI (RMSI). That is, the RMSI may refer to the SIB1.

The MIB includes information necessary for decoding SIB1. For example,the MIB may include information on a subcarrier spacing applied to SIB1(and MSG 2/4 used in the random access procedure, other SI), informationon a frequency offset between the SSB block and the subsequentlytransmitted RB, information on a bandwidth of the PDCCH/SIB, andinformation for decoding the PDCCH (e.g. information onsearch-space/control resource set (CORESET)/DM-RS, etc., which will bedescribed later). The MIB may be periodically transmitted, and the sameinformation may be repeatedly transmitted during 80ms time interval. TheSIB1 may be repeatedly transmitted through the PDSCH. The SIB1 includescontrol information for initial access of the UE and information fordecoding another SIB.

PDCCH decoding in NR is described. The search space for the PDCCHcorresponds to an area in which the UE performs blind decoding on thePDCCH. In LTE/LTE-A, the search space for the PDCCH is divided into acommon search space (CSS) and a UE-specific search space (USS). The sizeof each search space and/or the size of a control channel element (CCE)included in the PDCCH are determined according to the PDCCH format.

In NR, a resource-element group (REG) and a CCE for the PDCCH aredefined. In

NR, the concept of CORESET is defined. Specifically, one REG correspondsto 12 REs, i.e. one RB transmitted through one OFDM symbol. Each REGincludes a DM-RS. One CCE includes a plurality of REGs (e.g. 6 REGs).The PDCCH may be transmitted through a resource consisting of 1, 2, 4,8, or 16 CCEs. The number of CCEs may be determined according to theaggregation level. That is, one CCE when the aggregation level is 1, 2CCEs when the aggregation level is 2, 4 CCEs when the aggregation levelis 4, 8 CCEs when the aggregation level is 8, 16 CCEs when theaggregation level is 16, may be included in the PDCCH for a specific UE.

The CORESET may be defined on 1/2/3 OFDM symbols and multiple RBs. InLTE/LTE-A, the number of symbols used for the PDCCH is defined by aphysical control format indicator channel (PCFICH). However, the PCFICHis not used in NR. Instead, the number of symbols used for the CORESTmay be defined by the RRC message (and/or PBCH/SIB1). Also, inLTE/LTE-A, since the frequency bandwidth of the PDCCH is the same as theentire system bandwidth, so there is no signaling regarding thefrequency bandwidth of the PDCCH. In NR, the frequency domain of theCORESET may be defined by the RRC message (and/or PBCH/SIB1) in a unitof RB.

In NR, the search space for the PDCCH is divided into CSS and USS. Sincethe USS may be indicated by the RRC message, an RRC connection may berequired for the UE to decode the USS. The USS may include controlinformation for PDSCH decoding assigned to the UE.

Since the PDCCH needs to be decoded even when the RRC configuration isnot completed, CSS should also be defined. For example, CSS may bedefined when a PDCCH for decoding a PDSCH that conveys SIB1 isconfigured or when a PDCCH for receiving MSG 2/4 is configured in arandom access procedure. Like LTE/LTE-A, in NR, the PDCCH may bescrambled by a radio network temporary identifier (RNTI) for a specificpurpose.

A resource allocation scheme in NR is described. In NR, a specificnumber (e.g. up to 4) of bandwidth parts (BPWs) may be defined. A BWP(or carrier BWP) is a set of consecutive PRBs, and may be represented bya consecutive subsets of common RBs (CRBs). Each RB in the CRB may berepresented by CRB1, CRB2, etc., beginning with CRB0.

FIG. 7 shows an example of a frequency allocation scheme to whichtechnical features of the present invention can be applied. Referring toFIG. 7 , multiple BWPs may be defined in the CRB grid. A reference pointof the CRB grid (which may be referred to as a common reference point, astarting point, etc.) is referred to as so-called “point A” in NR. Thepoint A is indicated by the RMSI (i.e. SIB1). Specifically, thefrequency offset between the frequency band in which the SSB block istransmitted and the point A may be indicated through the RMSI. The pointA corresponds to the center frequency of the CRB0. Further, the point Amay be a point at which the variable “k” indicating the frequency bandof the RE is set to zero in NR. The multiple BWPs shown in FIG. 7 isconfigured to one cell (e.g. primary cell (PCell)). A plurality of BWPsmay be configured for each cell individually or commonly.

Referring to FIG. 7 , each BWP may be defined by a size and startingpoint from

CRB0. For example, the first BWP, i.e. BWP #0, may be defined by astarting point through an offset from CRB0, and a size of the BWP #0 maybe determined through the size for BWP #0.

A specific number (e.g., up to four) of BWPs may be configured for theUE. At a specific time point, only a specific number (e.g. one) of BWPsmay be active per cell. The number of configurable BWPs or the number ofactivated BWPs may be configured commonly or individually for UL and DL.The UE can receive PDSCH, PDCCH and/or channel state information (CSI)RS only on the active DL BWP. Also, the UE can transmit PUSCH and/orphysical uplink control channel (PUCCH) only on the active UL BWP.

FIG. 8 shows an example of multiple BWPs to which technical features ofthe present invention can be applied. Referring to FIG. 8 , 3 BWPs maybe configured. The first BWP may span 40 MHz band, and a subcarrierspacing of 15 kHz may be applied. The second BWP may span 10 MHz band,and a subcarrier spacing of 15 kHz may be applied. The third BWP mayspan 20 MHz band and a subcarrier spacing of 60 kHz may be applied. TheUE may configure at least one BWP among the 3 BWPs as an active BWP, andmay perform UL and/or DL data communication via the active BWP.

A time resource may be indicated in a manner that indicates a timedifference/offset based on a transmission time point of a PDCCHallocating DL or UL resources. For example, the start point of thePDSCH/PUSCH corresponding to the PDCCH and the number of symbolsoccupied by the PDSCH/PUSCH may be indicated.

Carrier aggregation (CA) is described. Like LTE/LTE-A, CA can besupported in

NR. That is, it is possible to aggregate continuous or discontinuouscomponent carriers (CCs) to increase the bandwidth and consequentlyincrease the bit rate. Each CC may correspond to a (serving) cell, andeach CC/cell may be divided into a primary serving cell (PSC)/primary CC(PCC) or a secondary serving cell (SSC)/secondary CC (SCC).

Hereinafter, a method for generating a RS sequence according to anembodiment of the present invention is described.

The common PRB indexing may be defined for maximum number of PRBs for agiven numerology. The maximum number of PRBs may be defined pernumerology based on the maximum number of subcarriers that a UEsupports. Because the maximum system bandwidth can be up to 400 MHz,which may exceed the maximum number of PRBs for certain numerologies,signaling details may need to be clarified.

Generally, it may be desirable to minimize signaling overhead. In otherwords, if a single value can be signaled for all numerologies, it may bemore desirable. In this case, the value should be sufficiently large tocover the maximum system bandwidth which may exceed the maximum numberof PRBs. Furthermore, for alignment among numerologies, in order tominimize the overhead of signaling, virtual PRB 0, instead of physicalPRB 0, which can be outside of system bandwidth may be indicated. Thus,the offset value may be considerably large, and may be indicated as anumber of PRBs based on numerology of the SS block, because the SS blockis used as a reference to create PRB grid, i.e. common PRB indexing. Asthis may increase the overall number of PRBs for certain numerologiesbeyond its maximum capacity, separate offset per numerology may beconfigured. The separate offset per numerology may be signaled byUE-specific configuration when needed. If the numerology of the RMSI isdifferent from the numerology of the SS block, the offset for the RMSInumerology may be indicated only.

In summary, a common offset among different numerologies may beindicated, or separate offset per numerology may be indicated. Theoffset for RMSI numerology may be given in RMSI, and other offsets maybe indicated by UE-specific signaling.

Furthermore, forward compatibility when the maximum bandwidth isincreased should be considered. This may be related to the abovedescription, i.e. a UE can be indicated with a PRB which is beyond itsmaximum PRB. If the UE can be indicated with a PRB which is beyond itsmaximum PRB, what the maximum value a UE can expect is may beconsidered.

If larger maximum bandwidth is introduced in later releases, differentcommon PRB indexing for Rel-15 UEs and future release UEs may beconsidered. Common PRB indexing has two main purposes. One is toindicate frequency location within a carrier and the other is to be usedfor potential RS sequence generation. For the first purpose, i.e. toindicate frequency location within a carrier, different PRB indexing maybe used between UEs with different releases which may be ensured by thenetwork. For the second purpose, i.e. to be used for RS sequencegeneration, if the network wants to multiplex UEs with differentreleases, it may be considered in future release UEs without impactbackward compatibility. In this sense, any specific handling for forwardcompatibility regarding common PRB indexing may not be necessary.

However, in terms of RS sequence generation, more flexible approach maybe preferred. That is, the network may configure length and/or offset ofthe RS sequence, and a UE may apply RS sequence mapping in its first PRBwithin its configured BWP, instead of assuming that RS sequence isgenerated based on common PRB indexing. The first motivation is to allownetwork flexibility in terms of RS generation. For example, multipleshort sequences over system bandwidth, one long sequence, etc., may begenerated based on configured length and/or offset of the RS sequence.The second motivation is to support potentially better forwardcompatibility. For example, if PRB 0 of a UE is different from PRB 0 ofanother UE while the network wants to multiplex them together, it may bepreferable to generate RS sequence based on configured length and/oroffset of the RS sequence, instead of common PRB indexing.

In summary, in terms of RS generation, instead of relying on common PRBindexing, additional configuration of length and/or offset of RSsequence may be supported. Based on additional configuration of lengthand/or offset of RS sequence, the UE may apply the mapping of RSsequence to its lowest PRB.

FIG. 9 shows a method for generating a RS sequence by a UE according toan embodiment of the present invention. The present invention describedabove for UE side may be applied to this embodiment.

In step S900, the UE receives information on a length of the RS sequenceand information on an offset of the RS sequence from a network. In stepS910, the UE generates the RS sequence based on the information on thelength and the information on the offset.

The generating the RS sequence may comprise mapping the RS sequence in afirst PRB within a configured BWP based on the information on the lengthand the information on the offset. The UE may transmit the RS sequenceto the network.

Meanwhile, multiple RS sequences including the RS sequence may begenerated over a system bandwidth. Furthermore, a PRB 0 of the UE may bedifferent from a PRB 0 of another UE.

According to embodiment of the present invention shown in FIG. 9 , theUE can generate the RS sequence based on the configured length and/oroffset of the RS sequence, instead of common PRB indexing. According tothe prior art, when the RS sequence is generated based on the common PRBindexing and the RS sequence is to be mapped to a portion which isrelatively farther from the PRB 0 of the system bandwidth, the signalingoverhead may occur. However, by generating the RS sequence based on theconfigured length and/or offset of the RS sequence, such signalingoverhead can be avoided.

FIG. 10 shows a UE to implement an embodiment of the present invention.The present invention described above for UE side may be applied to thisembodiment.

A UE 1000 includes a processor 1010, a memory 1020 and a transceiver1030. The processor 1010 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 1010. Specifically, the processor 1010 controls thetransceiver 1030 to receive information on a length of a RS sequence andinformation on an offset of the RS sequence from a network, andgenerates the RS sequence based on the information on the length and theinformation on the offset.

The generating the RS sequence may comprise mapping the RS sequence in afirst PRB within a configured BWP based on the information on the lengthand the information on the offset. The processor 1010 may control thetransceiver 1030 to transmit the RS sequence to the network.

Meanwhile, multiple RS sequences including the RS sequence may begenerated over a system bandwidth. Furthermore, a PRB 0 of the UE may bedifferent from a PRB 0 of another UE.

The memory 1020 is operatively coupled with the processor 1010 andstores a variety of information to operate the processor 1010. Thetransceiver 1020 is operatively coupled with the processor 1010, andtransmits and/or receives a radio signal.

According to embodiment of the present invention shown in FIG. 10 , theprocessor 1010 can generate the RS sequence based on the configuredlength and/or offset of the RS sequence, instead of common PRB indexing.According to the prior art, when the RS sequence is generated based onthe common PRB indexing and the RS sequence is to be mapped to a portionwhich is relatively farther from the PRB 0 of the system bandwidth, thesignaling overhead may occur. However, by generating the RS sequencebased on the configured length and/or offset of the RS sequence, suchsignaling overhead can be avoided.

FIG. 11 shows a method receiving a RS sequence by a BS according to anembodiment of the present invention. The present invention describedabove for BS side may be applied to this embodiment.

In step S1100, the BS transmits information on a length of the RSsequence and information on an offset of the RS sequence to a UE. Instep S1110, the BS receives the RS sequence, which is generated based onthe information on the length and the information on the offset, fromthe UE.

The RS sequence may be mapped in a first PRB within a configured BWPbased on the information on the length and the information on theoffset. Multiple RS sequences including the RS sequence may be generatedover a system bandwidth. A PRB 0 of the UE may be different from a PRB 0of another UE.

According to embodiment of the present invention shown in FIG. 11 , thenetwork can flexibly configure the length and/or offset of the RSsequence. For example, the network may configure the UE to generatemultiple short sequences over system bandwidth and/or one long sequence,etc. In addition, forward compatibility can be supported. For example,the network can multiplex UEs with different PRB 0.

FIG. 12 shows a BS to implement an embodiment of the present invention.The present invention described above for BS side may be applied to thisembodiment.

ABS 1200 includes a processor 1210, a memory 1220 and a transceiver1230. The processor 1210 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 1210. Specifically, the processor 1210 controls thetransceiver 1230 to transmit information on a length of the RS sequenceand information on an offset of the RS sequence to a UE, and to receivethe RS sequence, which is generated based on the information on thelength and the information on the offset, from the UE.

The RS sequence may be mapped in a first PRB within a configured BWPbased on the information on the length and the information on theoffset. Multiple RS sequences including the RS sequence may be generatedover a system bandwidth. A PRB 0 of the UE may be different from a PRB 0of another UE.

The memory 1220 is operatively coupled with the processor 1210 andstores a variety of information to operate the processor 1210. Thetransceiver 1220 is operatively coupled with the processor 1210, andtransmits and/or receives a radio signal.

According to embodiment of the present invention shown in FIG. 12 , theprocessor 1210 can flexibly configure the length and/or offset of the RSsequence. For example, the processor 1210 may configure the UE togenerate multiple short sequences over system bandwidth and/or one longsequence, etc. In addition, forward compatibility can be supported. Forexample, the processor 1210 can multiplex UEs with different PRB 0.

The processors 1010, 1210 may include application-specific integratedcircuit

(ASIC), other chipset, logic circuit and/or data processing device. Thememories 1020, 1220 may include read-only memory (ROM), random accessmemory (RAM), flash memory, memory card, storage medium and/or otherstorage device. The transceivers 1030, 1230 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 1020, 1220 and executed by processors 1010, 1210. The memories1020, 1220 can be implemented within the processors 1010, 1210 orexternal to the processors 1010, 1210 in which case those can becommunicatively coupled to the processors 1010, 1210 via various meansas is known in the art.

Secondary cell (SCell) configuration and/or BWP activation according toan embodiment of the present invention is described.

When SCell is activated, it is necessary to allow DL and ULtransmissions for any necessary functions. Even though expected UEbehavior in SCell activation may need to be further discussed,generally, a UE is expected to be able to monitor control channels, andperform CSI feedbacks once SCell is activated. In that sense, it may benecessary to activate one DL BWP. For CSI feedback, as it may be donevia PCell, activation of UL BWP seems not essential. However, if theSCell has its associated UL or a UE is expected to perform random accessprocedure on SCell during activation, activation of UL BWP seemsnecessary as well. In other words, at SCell activation, either DL only(i.e. only active DL BWP) or DL/UL (i.e. both DL/UL active BWP) may beconfigured. Regarding supplemental (SUL) band as a SCell, a UE mayselect default UL BWP based on measurement or the network may configurewhich one in its activation. In summary, in SCell activation, DL BWP maybe activated only for DL only SCell, and DL/UL BWPs may be activated forDL/UL SCell.

Furthermore, for common PRB indexing in a SCell, it may be necessary tohave a reference frequency location and/or offset between the referencefrequency location and PRB 0. A simple approach is to configure thelowest frequency or center of default DL BWP as a reference frequencylocation, and indicate the offset from the PRB 0. Once a UE acquirescommon PRB indexing, common PRB indexing may be used for otherconfigurations (including other BWP configurations). In summary, incommon PRB indexing, a reference point to determine common PRB indexingmay be derived based on default BWP configuration.

To support this, the configuration of default BWP may be configured withcarrier/cell configuration.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope of the present disclosure.

What is claimed is:
 1. A method performed by a user equipment (UE) in awireless communication system, the method comprising: receiving, from anetwork, a synchronization signal (SS) block; identifying an offsetbetween the SS block and a remaining minimum system information (RMSI)control resource set (CORESET); identifying the RMSI CORESET based onthe offset; monitoring the identified RMSI CORESET; receiving, from thenetwork, an RMSI based on monitoring the RMSI CORESET; receiving, fromthe network, information on a length of a reference signal (RS) sequenceand information on an offset of the RS sequence; performing an RSsequence mapping to map the RS sequence to a physical resource block 0(PRB0) of the UE within a bandwidth part (BWP) based on the length ofthe RS sequence and the offset of the RS sequence; and transmitting, tothe network, the RS sequence, wherein the length of the RS sequence andthe offset of the RS sequence are used for the RS sequence mapping basedon that: the PRB0 of the UE is different from that of another UE withinthe BWP so that a common PRB indexing is unused for the RS sequencemapping.
 2. The method of claim 1, wherein multiple RS sequencesincluding the RS sequence are generated over a system bandwidth.
 3. Themethod of claim 1, wherein the UE is in communication with at least oneof a mobile device, a network, and/or autonomous vehicles other than theUE.
 4. A user equipment (UE) in a wireless communication system, the UEcomprising: a memory; a transceiver; and at least one processor,operably coupled to the memory and the transceiver, configured to:control the transceiver to receive, from a network, a synchronizationsignal (SS) block; identify an offset between the SS block and aremaining minimum system information (RMSI) control resource set(CORESET); identify the RMSI CORESET based on the offset; monitor theidentified RMSI CORESET; control the transceiver to receive, from thenetwork, an RMSI based on monitoring the RMSI CORESET; control thetransceiver to receive, from the network, information on a length of areference signal (RS) sequence and information on an offset of the RSsequence, perform an RS sequence mapping to map the RS sequence to aphysical resource block 0 (PRB0) of the UE within a bandwidth part (BWP)based on the length of the RS sequence and the offset of the RSsequence, and control the transceiver to transmit, to the network, theRS sequence, wherein the length of the RS sequence and the offset of theRS sequence are used for the RS sequence mapping based on that: the PRB0of the UE is different from that of another UE within the BWP so that acommon PRB indexing is unused for the RS sequence mapping.
 5. The UE ofclaim 4, wherein multiple RS sequences including the RS sequence aregenerated over a system bandwidth.
 6. A method performed by a basestation (BS) in a wireless communication system, the method comprising:transmitting, to a user equipment (UE), a synchronization signal (SS)block; identifying an offset between the SS block and a remainingminimum system information (RMSI) control resource set (CORESET);configuring the RMSI CORESET based on the offset; transmitting, to theUE, an RMSI based on the RMSI CORESET; transmitting, to the UE,information on a length of a reference signal (RS) sequence andinformation on an offset of the RS sequence; and receiving, from the UE,the RS sequence, wherein the RS sequence is mapped to a physicalresource block 0 (PRB0) of the UE within a bandwidth part (BWP)according to an RS sequence mapping, and wherein the length of the RSsequence and the offset of the RS sequence are used for the RS sequencemapping based on that: the PRB0 of the UE is different from that ofanother UE within the BWP so that a common PRB indexing is unused forthe RS sequence mapping.
 7. The method of claim 6, wherein multiple RSsequences including the RS sequence are generated over a systembandwidth.